Add "Alternate" mod to osu!taiko

[nobbele]

This PR adds an "Alternate" mod similar to the osu ruleset and complements taiko's singletap mod.

I've seen the old PR, I'm not exactly sure what code quality concerns there were there but I tried to make this cleaner.

Also, osu.Game.Rulesets.Osu.Mods.InputBlockingMod and the new osu.Game.Rulesets.Taiko.Mods.InputBlockingMod classes are very similar, I believe they could lifted up to osu.Game.Rulesets.Mods easily. I didn't wanna touch osu ruleset and engine code unnecessarily, but if it's ok I can add it to this PR.

[Natelytle]

Are you still interested in this PR? If so, there are a couple minor changes I'd like to propose, and getting this up to date would be nice because I'm interested in a mod like this getting in since the singletap and alternate mods have been ranked in standard and taiko already. If you aren't interested anymore I'm perfectly willing to take over this branch.

[peppy]

@Natelytle yes, there still seems to be interest to please bring this up-to-date and we'll give it another shot.